Emergency myocardial revascularization

Myocardial protection by a left ventricular assist device during reperfusion following acute coronary occlusion

To evaluate the effects of a left ventricular assist device (LVAD) during the reperfusion period following acute coronary occlusion, sixteen mongrel dog hearts were subjected to 1 hour's occlusion of the circumflex coronary artery and then reperfused for 6 hours. In seven control dogs (control group), the hearts were reperfused without any support. In nine LVAD dogs (LVAD group), however, the left ventricles were supported by the application of a pneumatic driven diaphragm-type pump for 5 hours and then reperfused for another hour without any device. Triphenyltetrazolium chloride was used to determine the extent of infarction. The results showed a significant reduction in the area of infarct (AI) as a percentage of the area at risk (AR) in the LVAD group compared with the control group, the AI/AR being 22.3 per cent for the control group versus 4.8 per cent for the LVAD group (p less than 0.05). The cardiac output was also significantly higher in the LVAD group compared with the control group. The per cent systolic shortening in the ischemic region of the LVAD group showed a significantly better recovery, being 75.8 per cent for the LVAD group versus 24.4 per cent for the control group (p less than 0.01). It was concluded that the application of a LVAD during reperfusion after 1 hour's coronary occlusion results in a significant reduction of infarct size and provides improvement in both regional and global cardiac function.

Randomized versus historical controls for clinical trials

To compare the use of randomized controls (RCTs) and historical controls (HCTs) for clinical trials, we searched the literature for therapies studied by both methods. We found six therapies for which 50 RCTs and 56 HCTs were reported. Forty-four of 56 HCTs (79 percent) found the therapy better than the control regimen, but only 10 of 50 RCTs (20 percent) agreed. For each therapy, the treated patients in RCTs and HCTs of the same therapy was largely due to differences in outcome for the control groups, with HCT control patients generally doing worse than the RCT control groups. Adjustment of the outcomes of the HCTs for prognostic factors, when possible, did not appreciably change the results. The data suggest that biases in patient selection may irretrievably weight the outcome of HCts in favor of new therapies. RCTs may miss clinically important benefits because of inadequate attention to sample size. The predictive value of each might be improved by reconsidering the use of p less than 0.05 as the significance level for all types of clinical trials, and by the use of confidence intervals around estimates of treatment effects.

Unstable angina pectoris. Factors influencing operative risk

Experience was reviewed with 471 consecutive patients who had coronary artery bypass (CAB) operation alone. The hospital mortality rate was 2% in 341 patients operated on for treatment of stable angina pectoris. There were ten deaths (7.7%) in the 130 patients who underwent CAB for treatment of unstable angina. In this series, age greater than 70 years, poor left ventricular function, distal coronary arteries unfavorable for grafting and the presence of main left coronary artery disease were factors associated with increased operative mortality. In 78 patients with unstable angina who had none of these increased risk factors, the mortality rate was 1.3%. Hospital mortality was 33% in patients older than 70 years and 29% in patients with poor left ventricular function and/or distal vessels unfavorable for grafting. In 23 of the 130 patients, the only increased risk factor present was severe stenosis of the main left coronary artery and one of them (4.3%) died. Thus, when elderly patients and patients with poor left ventricular function or poor distal vessels were excluded, the hospital mortality rate associated with CAB in patients with unstable angina was low (2.0%, 2/101 patients) and equal to that for operation in patients with stable angina pectoris.

The measurement and control of myocardial infarct size

Direct, chemical, electrocardiographic and radio-isotopic methods are described for the estimation of myocardial infarct size in animals and man. Their relative points and failings are discussed. The effects of interventions, physical, metabolic and pharmacological, upon the size of myocardial infarcts, are examined and work attempting to reduce myocardial infarct size in man reviewed.